docs: def select(self, columns=(), by=(), where=(), **kwds):
          """select from self
  
          >>> t = q('([]a:1 2 3; b:10 20 30)')
          >>> t.select('a', where='b > 20').show()
          a
          -
          3
          """
          return self._seu('select', columns, by, where, kwds)